Apoptosis regulated by a death factor and its receptor: Fas ligand and Fas.

Homeostasis in vertebrates is tightly regulated by not only proliferation and differentiation of cells, but also cell death or apoptosis (Ellis et al. 1991; Raff 1992). Many cytokines bind to their respective receptors to regulate proliferation and differentiation of cells. Our recent studies on the Fas ligand and Fas indicate that they work respectively as a death factor and its receptor and suggest that, in some cases, cell death or apoptosis is regulated by cytokines and their receptors. Here, I present the summary of the Fas/Fas ligand system which has been studied in my laboratory over the past 5 years, and I will discuss its physiological roles.